Scientific American columns

Evolution helps us imagine what aliens might be like

What are the odds that intelligent, technically advanced aliens would look anything like the ones in films, with an emaciated torso and limbs, spindly fingers and a bulbous, bald head with large, almond-shaped eyes? What are the odds that they would even be humanoid? In this YouTube video, produced by Josh Timonen of the Richard Dawkins Foundation for Reason and Science, I argue that the chances are close to zero. Richard Dawkins himself made this interesting observation in a private communication after viewing it:

I would agree with [Shermer] in betting against aliens being bipedal primates, and I think the point is worth making, but I think he greatly overestimates the odds against. [University of Cambridge paleontologist] Simon Conway Morris, whose authority is not to be dismissed, thinks it positively likely that aliens would be, in effect, bipedal primates. [Harvard University biologist] Ed Wilson gave at least some time to the speculation that, if it had not been for the end-Cretaceous catastrophe, dinosaurs might have produced something like the attached [referring to paleontologist Dale A. Russell’s illustrated evolutionary projection of how a bipedal dinosaur might have evolved into a reptilian humanoid].

I replied to Dawkins that if something like a smart, technological, bipedal humanoid has a certain level of inevitability because of how evolution unfolds, then it would have happened more than once here. In his 2001 book Nonzero: The Logic of Human Destiny, Robert Wright argues that our existence precludes other terrestrial intelligences of our level from arising. But Neandertals were as close as one can get to a counterfactual experiment: they had hundreds of thousands of years to themselves in Europe without our interference and showed nothing like the technological and cultural progress of the modern humans who displaced them. Dawkins’s rejoinder to me is enlightening:

But you are leaping from one extreme to the other. In the film vignette, you implied a quite staggering rarity, so rare that you don’t expect two humanoid life-forms in the entire universe. Now you are … pointing out, correctly, that a certain inevitability would predict that humanoids should have evolved more than once on Earth! So, yes, we can say that humanoids are fairly improbable, but not necessarily all that improbable! Anything approaching “a certain inevitability” would mean millions or even billions of humanoid life-forms in the universe, simply because the number of available planets is so huge. Now, my guess is intermediate between your two extremes … I suspect that humanoids are not so very rare as to justify the statistical superlatives that you permitted yourself in the vignette.

Good point. But of the 60 to 80 phyla of animals, only one, the chordates, led to intelligence, and only the vertebrates actually developed it. Of all the vertebrates, only mammals evolved brains big enough for higher intelligence. And of the 24 orders of mammals only one — ours, the primates — has technological intelligence. As the late Harvard evolutionary biologist Ernst Mayr concluded: “Nothing demonstrates the improbability of the origin of high intelligence better than the millions of phyletic lineages that failed to achieve it.” In fact, Mayr calculated that even though there have evolved perhaps as many as 50 billion species on Earth, “only one of these achieved the kind of intelligence needed to establish a civilization.”

The late astronomer Carl Sagan, in a Planetary Society debate with Mayr (Bioastronomy News, Vol. 7, No. 4, 1995), noted that technologically communicating species “may live on the land or in the sea or air. They may have unimaginable chemistries, shapes, sizes, colors, appendages and opinions. We are not requiring that they follow the particular route that led to the evolution of humans. There may be many different evolutionary pathways, each unlikely, but the sum of the number of pathways to intelligence may nevertheless be quite substantial.”

Thus, the probability of intelligent life evolving elsewhere in the cosmos may be very high even while the odds of it being humanoid may be very low. I strongly suspect that we are blinded by Protagoras’ bias (“Man is the measure of all things”) when we project ourselves into the alien Other.

5 Comments to “Will E.T. Look Like Us?”

There is a hypothesis for Intelligent Design, but I doubt even the Intelligent Design community are aware of it. This could be the classic example of scientists overlooking something, simply because it does not come from a scientifically credible source, as this hypothesis does. As I mentioned above it is about the progressive evolution of design by advanced science and NOT by nature or a super deity. Unlike evolution this allows for many issues to be contained in the same framework, rather than excluding issues such as history because it is not deemed relevant to the theory of evolution.If this hypothesis were correct, it would suggest that science has been in effect been retro-engineering what was done by advanced science over a considerably shorter period than evolution would allow, but much longer than that suggested by religious perspectives.So the evidence of progressive evolution of design hitherto presumed to be be nature, is in part is from from the work of these advance scientists and in addition to that from the many civilsations that have existed on this very ancient planet. Sounds incredible but as Sir Fred Hoyle said,’ it is not logical to reject something,simply because it is incredible’. Evolution theory has been an excellent way of breaking the stranglehold of the old understandings, however I feel we need an evolution of thinking, which allows for a logical connection between the past and what we are likely to be capable of now and in the near future. I have great confidence in science and the future ,with the work of Craig Ventner. He is near to becoming a creator of life. So now, with this new hypothesis we can re-examine old historical texts to find the traces of evidence, and in addition to consider the scientific predictions made by this hypothesis taking into account a much bigger picture. One can now, look at some of the information in those ancient texts as being intended for those scientists today,open minded enough to be able to understand, what is at stake.The condition of our humanity, and for that matter any humanity is scientifically predictable.When any humanity reaches the level of nuclear technology, in weapons of war, then that humanity enters that predictable phase of potential self-destruct. One can hardly argue with the current state of the world as it is, with population having grown by some 4.5 billions in 65 years, the number of nuclear weapons and the rapidly changing environment.I feel re the latter two points, this coincides with the same concerns as Bulletin of Atomic Scientists. So in the words of Montaigne ,’ Let nothing pass the sieve of understanding through mere confidence and authority’.

Sir, you seem to be wrong about everything and you negate fact right in front of you and you are always laughing at inappropriate places all the time. I question your intent and I feel as a scientist you are very close minded, I would love to debate you and I fear that I will win all points and have you flapping in the breeze as it were. I have never lost any argument using logic, etc. I know how that sounds yet I am adamant on this and have many who would agree with me, please advise me as to your willingness for a friendly argument, I know I would enjoy it and you might also but you will be losing and I am sorry about that but I must correct your thoughts which are clearly wrong on what seems to be everything and I do not enjoy your waves of wrong intent that go out to everyone.

I have come to this facinating exchange a bit late. I have a couple of interesting questions of my own, directed at the question of Artificial Intellegence (AI), but that could no doubt have larger implications.

1) Other intelligent beings probably exist.
2) At least one is billions of years ahead of us.
3) It probably has the power to direct the universe at will.

If the above is correct, then human existence is in a sense at the grace of this being. If that is the case, then evolution does not occur without its direction, or at least tacit permission.

Is this a Creationist argument? Should this convince us to act as if there is a God, since it is scientifically probable? I am neither religious or Creationist, but I find this argument relatively convincing.

Well, I’ll be sure my comment reflects ideas inspired by the actual subject of your post. I’m just wondering how this estimate of probabilities even makes sense. For starters, I agree that anthropomorphizing probably explains the appearance of our alleged alien visitors; I’ll even be controversial and say that Russell’s pictures strike me as incomprehensibly absurd, a perfect manifestation of Plato’s observation and many far less sophisticated human inclinations.

That said, I don’t understand how you can honestly claim that the probability of intelligent life being bipedal is so low. A probability of 1:5E10 of intelligent life evolving into bipedal creatures may seem like an incredible thing when thinking about this one planet, in this one solar system. But given the fact that despite the mighty potential of our intellects, humanity cannot directly observe the same “Goldie Locks” zone we are nearly certain is the essential range for life-producing planets in the system surrounding our closest solar neighbor! Not only CAN’T we determine that life doesn’t thrive around EVERY planet within that range around ALL Sun-like stars, but we can’t even determine that intelligent life, with the EXACT same technological limitations as our own, don’t exist as well. After all, if we’re too primitive to observe them, they can’t observe us. It baffles me why so many thinking-people talk about how absurd it is that life could have evolved into a similar form elsewhere within a similar time frame when it did exactly that in the only sample we can observe.

More to the point of the post, though, even acknowledging that by now we would have likely received some sort of indication if life at least as advanced as us were thriving around solar systems within 70 light years of the sun, we still are in no position to determine the probability of life having evolved there in the same abundance as it has on Earth. And given that we can’t even make that assessment, we are utterly incapable of producing realistic estimates on the anatomical nature of any other life-producing planet’s most intelligent creatures. The reason is simple: assume that a tiny fraction of the 10E23 stars in the universe are sun-like, and a fraction of those have evolved life in their Goldie Locks zones as they have in our only sample, then the incredible-seeming probability of bipeds being the form intelligent life would take becomes…well, do the math. :)